The mononitro derivatives in positions .alpha. and .beta. of anthraquinone are important intermediates in the manufacture of dyestuffs. It is known that .alpha.-nitroanthraquinone may be obtained by nitration of anthraquinone, but this reaction leads to the unavoidable formation of dinitro derivatives which first have to be eliminated in order to recover the desired anthraquinone. It is also known to prepare 2-nitro-1,4,4a,9a-tetrahydro-anthraquinone by the nitration of 1,4,4a,9a-tetrahydro-anthraquinone as described in Japanese Pat. No. 77,108,429. However, this method does not result in a mononitro derivative capable of yielding the subsequent .alpha.-nitro-anthraquinone.